1. Technical Field
The present invention relates to a light emitting diode (LED) printer, and more particularly, to a mechanism for changing the process unit thereof.
2. Background Art
Conventional designs of printers relying upon light emitting diode arrays have pivotally connected upper and lower frames enclosing a photosensitive drum and developer assembly, a fixer, and a paper conveying assembly. U.S. Pat. No. 3,985,436 for example, mentions a photo processing unit having a cleaning device, photo-sensitive drum, electric charger, and developer. An LED frame is manually opened and closed by pivoting upon a hinge. In order to change the process unit, the upper body frame is first opened, and then a lever on the frame is pressed so as to release a hook engaging the upper body frame. Thus, the LED frame is opened upwardly in order to remove the process unit from the unit guide.
If however, the process unit is mounted in the unit guide and the frame including the LED head array is pivoted downwardly on the hinge, the book is held by the upper body frame so that the LED head array may be positioned facing the photo-sensitive drum through an opening formed in the upper part of the unit guide at a fixed interval therebetween. Such designs fail to accommodate a range of manufacturing tolerances as well as changes of tolerances occurring during usage attributable to wear and tear of, -for example, slight manufacturing misalignment or gradual wear of the hook engaging the upper body frame. Consequently, contemporary designs do not assume maintenance of a constant gap between the light emitting diode array and the photo-sensitive drum.
Such contemporary designs of conventional LED printers are complicated, and require manual disassembly and reassembly of the related component parts in order to change the process unit.